"Okko's Inn" centers on Oriko Seki, a young girl who, after losing her parents in a car accident, moves to her grandmother's traditional hot spring inn, Hananoyu. The inn is located in the countryside and has a long history of hospitality. Oriko, nicknamed Okko, begins to adjust to her new life under the guidance of her grandmother, who teaches her the responsibilities of running the inn.

As Okko settles in, she discovers that the inn is inhabited by friendly spirits, including Uribo, a mischievous ghost boy, and Miyo, a cheerful ghost girl. These spirits assist Okko in her duties and help her navigate the challenges of managing the inn. The presence of these spirits adds a supernatural element to the story, blending the everyday tasks of innkeeping with fantastical encounters.

Throughout the series, Okko interacts with various guests, each bringing their own stories and challenges. These interactions highlight themes of empathy, resilience, and the importance of community. Okko's growth is evident as she learns to balance her grief with her new responsibilities, finding strength in her relationships with both the living and the spirits.

The narrative also explores the cultural aspects of running a traditional Japanese inn, emphasizing the values of hospitality and respect. Okko's journey is one of self-discovery, as she gradually comes to terms with her loss and finds a sense of purpose in her role at Hananoyu. The series balances emotional depth with lighthearted moments, creating a heartfelt story that resonates with viewers of all ages.